Patches 26 bugs, including several that pose serious threat to Windows users

For the second time in the last four months, Microsoft today shipped a record 13 security updates that patched dozens of vulnerabilities in Windows.

The 26 flaws fixed today were off the record of 34 set in October 2009 when Microsoft last issued 13 security bulletins. However, if Microsoft had waited until today to deliver the rush Internet Explorer (IE) update it released late last month -- the IE patches were original slated to appear as part of today's collection -- this month's lot would have tied the vulnerability record.

Five of the 13 updates were marked "critical," the highest threat ranking in Microsoft's four-step scoring system. Seven were ranked "important," the next-lower rating, while one was pegged "moderate." Eleven of the 13 affected Windows, while the remaining pair impacted Office XP and Office 2003 on Windows and Office 2004 for Mac.

Three of the updates stood out immediately, said Andrew Storms, director of security operations at nCircle Network Security, including one related to DirectShow, a component of Windows' DirectX graphics infrastructure; and two involving SMB (Server Message Block), the Microsoft-made network file and print-sharing protocol.

"The DirectShow vulnerability in MS10-013 has the potential for a classic drive-by attack," said Storms, who noted that the flaw is in Windows' parsing of .avi movie files. "There's no shortage of people watching video on the Web," Storms said, adding that he put the update on his short list because of the potential for large-scale attacks.

Microsoft agreed, tagging the update as critical and betting that attackers will come up with reliable exploits for the bug in the next 30 days.

Storms' other must-patch updates were a pair related to SMB: MS10-006on the client side and MS10-012 on the server side.

Other than the historical nature of those updates -- Microsoft quashed six bugs in SMB last year on two different Patch Tuesdays -- Storms pointed out that Microsoft believes the flaws serious, more dangerous apparently than the SMB vulnerability it didn't fix today, even though that bug has exploit code in circulation.

"Microsoft's saying that these patches are much more important, even though there is public code out there for the denial-of-service," Storms said, referring to the outstanding security advisory for an SMB flaw that it said last week it wouldn't fix today. "Usually the big attack vector is on the server side [for SMB], since they're typically network-based attacks," he continued. "We haven't been too worried about them because of default firewalls, but this month we're seeing vulnerabilities on the client side as well."

Other updates patched PowerPoint, Office's presentation maker; Microsoft Paint, the bare bones paint program included with all versions of Windows; the operating system's implementation of TCP/IP; Windows Server 2008's Hyper-V virtualization software; the Windows kernel; and other bits and pieces of Windows.

The kernel update, MS10-015, patched the 17-year-old bug in all 32-bit versions of Windows that went public Jan. 19 when a Google engineer disclosed the vulnerability on a security mailing list.

As announced last week, Microsoft today did not patch an IE bug it only recently confirmed.

This month's security update can be downloaded and installed via the Microsoft Update and Windows Update services, as well as through Windows Server Update Services.